At least 26 people are dead and 100 more were injured Saturday after a train derailed between Moscow and St. Petersburg. Authorities say a homemade bomb on the tracks caused the tragedy, but no group has claimed responsibility for the attack. Witnesses said they agreed that a bomb probably caused the derailment, and police have restricted access to the bomb crater. More than a dozen people are still missing. President Dmitry Medvedev called for calm, saying "we need there to be no chaos, because the situation is tense as it is.” In 2007, a deadly explosion caused a derailment on the same line and was ruled a terrorist attack. More than 600 people were aboard the train.